High-pressure device

ABSTRACT

This invention relates to high-pressure dies normally used for use in the synthesis of diamonds. The die comprises a die ring having a through cavity within which there is formed a pressure chamber that is lined with a pyrophyllite sleeve. Respectively entering the ends of the sleeve are two plungers. These plungers are capable of sliding in the sleeve until near the end of their compressive strokes so that little or no axial pressure is applied to the ends of the sleeve.

United States Patent Pope et al.

[451 Feb. 15,1972

[54] HIGH-PRESSURE DEVICE [72] Inventors: Noel C. Pope; Edward B. Kempis; Kevin H. J. ODonovan, all of Johannesburg,

Republic of South Africa [73] Assignee: Adamant Laboratories (Proprietary) Limited I221 Filed: Sept. 30, 1969 m Appl. No; 2402.415

IS2| 11.5. (11 ..425/356 I51 I Int. Cl. ..B29c 3/00 [58] FieldofSearch ..18/16.5,l6R,16E,16F,

18/16 H, 16.7, DIG. 26, DIG. 43

[56] References Cited UNITED STATES PATENTS 2,947,609 8/ 1960 Strong ..l8/ 16.5

2,992,900 7/ 1961 Bovenlark l 8/D1G. 26 3,075,245 1/1963 Bundy ..18/16.5 3,212,853 10/1965 Wentorf, Jr. et a1. 18/16.5 X

Primary Examiner-Robert L. Spicer, Jr. Attorney-Waters, Roditi,.Schwartz & Nissen [57] ABSTRACT This invention relaten to high-pressure dies normally used for use in the nynthcuis of diamonds. The die comprineu a die ring having a through cavity within which there is formed a pressure chamber that is lined with a pyrophyllite sleeve. Respectively entering the ends of the sleeve are two plungers. These plungers are capable of sliding in the sleeve until near the end of their compressive strokes so that little or no axial pressure is applied to the ends of the sleeve.

7 Claims, 1 Drawing Figure This invention relates to dies, capable of generating pressures of a very high order, and comprising a dished die ring within the cavity of which the pressure chamber is located, and at least one plunger which operates to diminish the volume of the pressure chamber and thereby compress its contents. Conventionally, dies of this sort have opposed plungers which move inwardly to compress a capsule in the pressure chamber.

The commonest application of these dies in current technology is to the synthesis of diamond, and, for this purpose, provision must be made for heating the charge in the capsule to produce within the chamber the conditions of temperature and pressure which will bring the charge into the diamond-stable region of the graphite-diamond equilibrium diagram. Heating is effected by passing an electric current through the charge, and it is therefore necessary to insulate the charge electrically as well as thermally. The means employed includes a sleeve, e.g., of pyrophyllite, which lines the cavity of the die ring and which defines the pressure chamber.

All known high-pressure, high-temperature dies of which we are aware are so arranged that the load applied by the piston is imposed both upon the capsule within the pressure chamber and upon the insulating sleeve.

The pressure generated within the pressure chamber is directly dependent upon the press load that is brought to bear upon the charge. in known dies, the press load is divided between the charge and the insulated sleeve surrounding it.

The proportion of the load applied to the sleeve is wasted.

This waste may be minimized by using a grade of pyrophyllite which is readily compressible, but then the mounting pressure within the capsule causes the sleeve to bulge outwardly, which causes a pressure loss in the charge. A harder grade of pyrophyllite to minimize radial bulging means that a greater proportion of the press load is absorbed in squeezing the sleeve. That is the dilemma which the user of the conventional die faces, and which it is the object of the present invention to resolve.

According to the invention, the plunger or each plunger is shaped to penetrate into the sleeve without significant axial compression of the sleeve.

Further according to the invention, the plunger is composed of a cylindrical end the diameter of which is substantially that of the internal diameter of the sleeve and the length of which exceeds the stroke of the plunger, so that no compressive force in the axial direction of the sleeve is imposed upon it. The consequence of this construction is that the sleevecan be made as hard and as incompressible as possible, to minimize radial give under the bursting pressures imposed on the sleeve by the capsule.

Extrusion of the capsule and the charge between the sleeve and the plunger must be minimized, because loss of material from the pressure chamber means loss of pressure. To this end, a gasket is inserted between the or each plunger and the dished face or faces of the die ring, which is compressed as the die closes, to constitute a seal against extrusion. This gasket has the further effect of acting as a stop or buttress to prevent crumbling of the sleeve ends.

Preferably, the plunger includes a radial flange which engages the outer end of the gasket to restrain its outward movement under the mounting pressure. As the die closes the flange is bent back against the plunger and is overlainby the compressed gasket to preserve the electrical isolation of the plunger from the die ring.

A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawing which isa section through a device ofthe invention with the parts in the upper portion of the drawing above line XX being in the setup position is the-position which they take up before applyingpressure and the parts in the lower portion below the line XX in the position which they take up after applying pressure.

Referring now to the drawing there is shown a die of the invention for use in the synthesis of diamonds. The die comprises a die ring 10 having a dished through opening 12 which has converging faces 13 leading from its ends to a central cylindrical portion 14 forming a pressure chamber. The major portion of this cylindrical portion 14 is lined with a pyrophyllite sleeve 16. A pair 1 of opposed frustoconical anvils 18 are arranged coaxially in an hydraulic press (not shown) and located one at each end of the opening 12. One of the anvils, normally the lower anvil, is moved towards the other to apply pressure to the pressure chamber.

On the flat inside face 20 of each anvil there is mounted the base 22 of a steel plunger 24 having a hollow cylindrical portion 26 which fits the interior of the sleeve 16 and which is packed with a thermal insulating material such as pyrophyllite. A flange 30, forming a continuation of the base 22, surround the plunger 24, and projects beyond the sides of the anvil. At the join of and merging into the outside of the cylindrical portion 26 and the flange 30 there is provided a frustoconical shoulder or gusset 32 having the same cone angle as the anvil l8 and conveniently lying on the continuation of the cone containing the outside surface of the anvil 18.

The axial height of the gusset 32 is small as compared to the axial height of the cylindrical portion. The axial length of the cylindrical outside surface of the portion 26 is slightly more than half the pressure stroke of the movable anvil. The inside end of each portion 26 projects into the sleeve 16 for setupof the die and the length of the remaining or outside portion is slightly less than half the pressure stroke. Thus during the major portion of the stroke the plunger will be sliding in the sleeve. It is only when the gusset or shoulder 32 engages the ends of the sleeve 16 that there will be any axial forces applied directly to the sleeve 16 by the plungers 22.

The capsule 36 is contained within the sleeve 16 between the plungers 24.

When the die closes, as seen in the lower portion of the figure, the capsule 36 is compressed and also the gaskets 34 are progressively squeezed and flattened between the converging faces 13 of the die ring 10 and the sides of the anvils 18. The flanges 30 act to restrain flow of the gaskets away from the sleeve 16 and eventually are bent over against the anvil l8. I

It will be observed that, as during the closing of the die, the plungers 22 slide in the sleeve 16, the entire press load is taken by the capsule 36 and that none of it is dissipated on the sleeve 16, until right at the end of the closing movement, when the gusset or shoulder 32 on the plunger 22 comes into contact with the corner of the sleeve 16.

This more effective use of the press load, relatively to conventional technique, either i. enables greater pressures to be generated within the capsule with the same press load, or

ii. permits a lower load to be used for the same generated pressure thus materially increasing the length of anvil life.

The invention is not limited to the precise constructional details herein described and shown in the drawings and its spirit 'and scope are to be derived solely from the following claims.

We claim:

1. A die for generating a very high internal pressure comprising:

a. a die ring having an opening therethrough, which opening formsa pressure chamber-having ends and sides,

b. a sleeve lining the pressure chamber,

.c. a plungerentering each end of the chamber, each of the plungers having a portion fitting the sleeve and being slidable-therein to diminish the volume to the pressure chamber, and

d. a peripheral flange on each of the plungers, which said flange contacts the sides of the chamber and is distorted thereby during sliding movement of the plunger.

2. A die as claimed in claim 1 in which the plunger has a shoulder which contacts an end of the sleeve on completion of the sliding movement of the plunger.

the plunger is slightly greater than the stroke of the plunger.

6. A die as claimed in claim 1 in which the plunger is mounted on an anvil that moves towards the die ring.

7. A die as claimed in claim 1 in which the plunger is hollow and is packed with insulation material. 

1. A die for generating a very high internal pressure comprising: a. a die ring having an opening therethrough, which opening forms a pressure chamber having ends and sides, b. a sleeve lining the pressure chamber, c. a plunger entering each end of the chamber, each of the plungers having a portion fitting the sleeve and being slidable therein to diminish the volume to the pressure chamber, and d. a peripheral flange on each of the plungers, which said flange contacts the sides of the chamber and is distorted thereby during sliding movement of the plunger.
 2. A die as claimed in claim 1 in which the plunger has a shoulder which contacts an end of the sleeve on completion of the sliding movement of the plunger.
 3. A die as claimed in claim 1 in which the flange is a radial flange.
 4. A die as claimed in claim 1 further comprising a shoulder on the plunger which shoulder engages the end of the sleeve on completion of the sliding movement of the plunger and which merges into the flange.
 5. A die as claimed in claim 1 in which the said portion of the plunger is slightly greater than the stroke of the plunger.
 6. A die as claimed in claim 1 in which the plunger is mounted on an anvil that moves towards the die ring.
 7. A die as claimed in claim 1 in which the plunger is hollow and is packed with insulation material. 